RDF4J supports two query languages (SeRQL and SPARQL), as well as a set of fully streaming parsers and writers for most common RDF syntax formats, called Rio. It also includes two database implementations for RDF storage, the in-memory store and the Native store.

In addition to its primary use as a set of Java libraries, RDF4J also provides a Server web application that can be accessed as a web service for RDF database access, and a Workbench web application which provides a (web-based) client user interface for an RDF4J Server.